Thermocatalytic process for CO2-free production of hydrogen and carbon from hydrocarbons

ABSTRACT

A novel process and apparatus are disclosed for sustainable CO 2 -free production of hydrogen and carbon by thermocatalytic decomposition (dissociation, pyrolysis, cracking) of hydrocarbon fuels over carbon-based catalysts in the absence of air and/or water. The apparatus and thermocatalytic process improve the activity and stability of carbon catalysts during the thermocatalytic process and produce both high purity hydrogen (at least, 99.0 volume %) and carbon, from any hydrocarbon fuel, including sulfurous fuels. In a preferred embodiment, production of hydrogen and carbon is achieved by both internal and external activation of carbon catalysts. Internal activation of carbon catalyst is accomplished by recycling of hydrogen-depleted gas containing unsaturated and aromatic hydrocarbons back to the reactor. External activation of the catalyst can be achieved via surface gasification with hot combustion gases during catalyst heating. The process and apparatus can be conveniently integrated with any type of fuel cell to generate electricity.

This invention relates to the production of hydrogen, and in particularto a thermocatalytic process and apparatus for drastically reducedcarbon dioxide emission in the production of hydrogen and carbon fromfossil fuels and is a divisional of U.S. patent application Ser. No.09/824,437 filed Apr. 02, 2001, now U.S. Pat. No. 6,670,058 which claimsthe benefit of priority of U.S. Provisional Application Ser. No.60/194,828 filed Apr. 05, 2000.

BACKGROUND AND PRIOR ART

In the near- to medium-term future hydrogen production will continue torely on fossil fuels, primarily, natural gas (NG). On the other hand,conventional hydrogen production processes are among major sources ofanthropogenic CO₂ emissions into the atmosphere.

In principle, hydrogen can be produced from hydrocarbon fuels viaoxidative and non-oxidative conversion processes. Oxidative conversioninvolves the reaction of hydrocarbons with oxidants: water, oxygen, orcombination of water and oxygen (steam reforming, partial oxidation andautothermal reforming processes, respectively). As a first step, theseprocesses produce a mixture of hydrogen with carbon monoxide(synthesis-gas), which is followed by gas conditioning (water gas shiftand preferential oxidation reactions) and CO₂ removal stages. The totalCO₂ emissions from these processes (including stack gases) reaches up to0.4 m³ per each m³ of hydrogen produced. Non-oxidative route includesthermal decomposition (TD) (or dissociation, pyrolysis, cracking) ofhydrocarbons into hydrogen and carbon.

TD of natural gas has been practiced for decades as a means ofproduction of carbon black with hydrogen being a supplementary fuel forthe process (Thermal Black process). In this process hydrocarbon streamwas pyrolyzed at high temperature (1400° C.) over the preheated contact(firebrick) into hydrogen and carbon black particles. The process wasemployed in a semi-continuous (cyclic) mode using two tandem reactors.U.S. Pat. No. 2,926,073 to P. Robinson et al. describes the improvedapparatus for making carbon black and hydrogen from hydrocarbons bycontinuous thermal decomposition process. Kvaerner Company of Norway hasdeveloped a methane decomposition process which produces hydrogen andcarbon black by using high temperature plasma (CB&H process disclosed inthe Proc. 12^(th) World Hydrogen Energy Conference, Buenos Aires, 697,1998). The advantages of the plasmochemical process are high thermalefficiency (>90%) and purity of hydrogen (98 v. %), however, it is anelectric energy intensive process. Steinberg et al. proposed a methanedecomposition reactor consisting of a molten metal bath (Int. J.Hydrogen Energy, 24, 771, 1999). Methane bubbles through molten tin orcopper bath at high temperatures (900° C. and higher). The advantages ofthis system are: an efficient heat transfer to a methane gas stream,and, ease of carbon separation from the liquid metal surface by densitydifference. A high temperature, regenerative gas heater for hydrogen andcarbon production from NG has been developed by Spilrain et al. (Int. J.Hydrogen Energy, 24, 613, 1999). In this process, thermal decompositionof NG was conducted in the presence of a carrier gas (N₂ or H₂) whichwas pre-heated to 1627–1727° C. in the matrix of a regenerative gasheater.

There have been attempts to use catalysts to reduce the maximumtemperature of the TD of methane. Transition metals were found to bevery active in methane decomposition reaction; however, there was acatalyst deactivation problem due to carbon build up on the catalystsurface. In most cases, surface carbon deposits were combusted by air toregenerate the original catalytic activity. As a result, all carbon wasconverted into CO₂, and hydrogen was the only useful reaction product.For example, Callahan describes a catalytic reactor (fuel conditioner)designed to catalytically convert methane and other hydrocarbons tohydrogen for fuel cell applications (Proc. 26th Power Sources Symp. RedBank, N.J., 181, 1974). A stream of gaseous fuel entered one of tworeactor beds, where hydrocarbon decomposition to hydrogen took place at870–980° C. and carbon was deposited on the Ni-catalyst. Simultaneously,air entered the second reactor where the catalyst regeneration occurredby burning coke off the catalyst surface. The streams of fuel and airwere reversed for another cycle of decomposition-regeneration. Thereported process did not require water gas shift and gas separationstages, which was a significant advantage. However, due to cyclic natureof the process, hydrogen was contaminated with carbon oxides.Furthermore, no byproduct carbon was produced in this process. U.S. Pat.No. 3,284,161 to Pohlenz et al. describes a process for continuousproduction of hydrogen by catalytic decomposition of a gaseoushydrocarbon streams. Methane decomposition was carried out in afluidized bed catalytic reactor in the range of temperatures from 815 to1093° C. Supported Ni, Fe and Co catalysts (preferably Ni/Al₂O₃) wereused in the process. The coked catalyst was continuously removed fromthe reactor to the regeneration section where carbon was burned off, andthe regenerated catalyst was recycled to the rector. U.S. Pat. No.2,476,729 to Helmers et al. describes the improved method for catalyticcracking of hydrocarbon oils. It was suggested that air is added to thefeedstock to partially combust the feed such that the heat supplied isuniformly distributed throughout the catalyst bed. This, however, wouldcontaminate and dilute hydrogen with carbon oxides and nitrogen.

Use of carbon catalysts offers the following advantages over metalcatalysts: (i) no need for the regeneration of catalysts by burningcarbon off the catalyst surface; (ii) no contamination of hydrogen bycarbon oxides; and, (iii) carbon is produced as a valuable byproduct ofthe process. Earlier, Muradov has reported on the feasibility of usingdifferent carbon catalysts for methane decomposition reaction (Proc.12^(th) World Hydrogen Conf., Buenos Aires, Argentina, 1998). It hasalso been taught to thermally decompose hydrocarbon feedstock overcarbon particles acting as a heat carrier. U.S. Pat. No. 2,805,177 toKrebs describes a process for producing hydrogen and product coke viacontacting a heavy hydrocarbon oil admixed with a gaseous hydrocarbonwith fluidized coke particles in a reaction zone at 927–1371° C. Gaseousproducts containing at least 70 v. % of hydrogen were separated from thecoke, and a portion of coke particles was burnt to supply heat for theprocess; the remaining portion of coke was withdrawn as a product. U.S.Pat. No. 4,056,602 to Matovich deals with high temperature thermalreactions, including the decomposition of hydrocarbons, by utilizingfluid wall reactors. Thermal decomposition of methane was conducted at1260–1871° C. utilizing carbon black particles as adsorbents of highflux radiation energy, and initiators of the pyrolytic dissociation ofmethane. It was reported that 100% conversion of methane could beachieved at 1815° C. at a wide range of flow rates (28.3–141.5 l/min).U.S. Pat. No. 5,650,132 to Murata et al. produces hydrogen from methaneand other hydrocarbons by contacting them with fine particles of acarbonaceous material obtained by arc discharge between carbonelectrodes and having an external surface area of at least 1 m²/g.Carbonaceous materials also included: soot obtained from the thermaldecomposition of different organic compounds or the combustion of fuels;carbon nanotubes; activated charcoal; fullerenes C₆₀ or C₇₀; and, finelydivided diamond. The optimal conditions for methane conversion included:methane dilution with an inert gas (preferable methane concentration:0.8–5% by volume); A temperature range of 400–1,200° C.; and residencetimes of −50 sec. An increase in methane concentration in feedstock from1.8 to 8 v. % resulted in a drastic drop in methane conversion from 64.6to 9.7% (at 950° C.). It was also stated that during hydrocarbonpyrolysis (the experiments usually ran for 30 min) the carbon samplesgradually lost their catalytic activity. It was suggested that oxidizinggases like H₂O or CO₂ be added to the pyrolyzing zone to improve thecatalyst life. However, this would inevitably contaminate hydrogen withcarbon oxides and require an additional purification step. Also, it wassuggested that the spent catalyst be combusted, which would be, however,very wasteful, especially, considering the high cost of the carbonmaterials used in the process. U.S. Pat. Nos. 1,528,905; 2,367,474;4,256,606; 4,615,993; 5,300,468 and 5,254,512 taught the differentmethods of regeneration of spent carbonaceous materials (CM), includingactivated carbons. However, these methods were mostly concerned with thereactivation of CM via removal (or displacement or decomposition) of theimpurities (or adsorbable substances) from the surface of CM.

In summary of the foregoing, the major problem with the decomposition ofmethane (or other hydrocarbons) over carbon (or any other) catalystsrelates to their gradual deactivation during the process. This could beattributed to two major factors: (i) loss of active surface area; and,(ii) inhibition of the catalytic process by the deposition of carbonspecies which are less catalytically active than the original carboncatalyst.

Thus, the need exists for a more effective, versatile and cost effectiveprocess for CO₂-free production of hydrogen and carbon from differenthydrocarbons using inexpensive and readily available catalyticmaterials.

SUMMARY OF THE INVENTION

It is a primary objective of the present invention to develop asustainable process for CO/CO₂-free production of hydrogen and carbon bythermocatalytic decomposition (pyrolysis, cracking) of hydrocarbonfuels.

A second object of this invention is to provide a process for thecontinuous production of hydrogen and carbon via thermocatalyticdecomposition of hydrocarbon feedstock over carbon-based catalysts.

A third object of this invention is to provide a process for hydrogenand carbon production from any gaseous or liquid hydrocarbon fuelincluding, but not limited to, methane, propane, gasoline, kerosene,diesel fuel, residual oil and crude oil.

A fourth object of the invention is to provide a process for thecontinuous production of hydrogen and carbon using internally andexternally activated carbon catalysts.

A fifth object of the invention is to provide a process for theproduction of hydrogen and carbon from sulfurous hydrocarbon fuelswithout additional purification of the feedstock.

A sixth object of the invention is to integrate the thermocatalyticreactor with a fuel cell for the production of electricity.

A preferred embodiment of the invention is a process for sustainableCO₂-free production of hydrogen and carbon via continuousthermocatalytic decomposition of hydrocarbons over a carbon-basedcatalyst in air and/or water-free environment, employing continuousreactivation of the catalyst, comprising the steps of: thermocatalyticdecomposition of hydrocarbon stream over a moving bed of carbonparticulates; recovering a stream of hydrogen-containing gas (HCG);directing said stream to a gas separation unit (GSU) where pure hydrogenis separated from said stream and hydrogen-depleted gas (HDG);recovering pure hydrogen; and, recycling said hydrogen-depleted gas tothe reactor whereby the catalytically active carbon is generated on thesurface of said original carbon catalyst. An apparatus is also describedfor carrying out the above identified process and its use in combinationwith a fuel cell for generation of electricity.

Further objects and advantages of this invention will be apparent fromthe following detailed description of a presently preferred embodiment,which is illustrated schematically in the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of an apparatus for carrying out theprocess of the invention.

FIG. 2 is a schematic diagram of an apparatus integrated with a fuelcell.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Before explaining the disclosed embodiment of the present invention indetail it is to be understood that the invention is not limited in itsapplication to the details of the particular arrangement shown since theinvention is capable of other embodiments. Also, the terminology usedherein is for the purpose of description and not of limitation.

Each numerically identified element of the apparatus in FIGS. 1 and 2 isdescribed below:

-   1—the reactor wherein the thermocatalytic decomposition of hydrogen    fuels is accomplished on a moving bed using carbon-based catalysts.    The reactor is interchangeably referred to herein as,    “thermocatalytic reactor”, “fluidized bed reactor”, “catalytic    reactor” and “reactor.”-   2—cyclone-   3—heat exchanger-   4—gas separation unit-   5—grinder-   6—heater-   7—fuel cell-   8—membrane gas separation unit-   9—anode compartment-   10—cathode compartment-   11—electricity

According to this invention, the above objects can be achieved bythermocatalytic decomposition of hydrocarbon fuels in a moving bedreactor using carbon-based catalysts in air and/or water-freeenvironment. The advantages and features of the present invention willbe apparent upon consideration of the following description. The novelprocess for producing relatively pure hydrogen is based on a single-stepthermocatalytic decomposition of hydrocarbons, preferably natural gas,over carbon-based catalysts in the absence of air and/or water accordingto the preferred (a) process and the generic (b) process as follows:

-   -   (a) CH₄→C+2H₂+75.6 kJ/mol; and,    -   (b) C_(n)H_(m)→nC+m/2H₂ wherein n is equal or greater than 1,        and m is equal or less than (2n+2), and the reaction is        endothermic.

The novelty of this approach completely eliminates the production ofundesired contaminants, CO and CO₂, in the production of pure hydrogenand, consequently, the need for water gas shift reaction, CO₂ separationand H₂ purification steps required by conventional technologies (e.g.methane steam reforming, partial oxidation, and the like). The process(a) is moderately endothermic (37.8 kJ/mole of H₂), so that about 10% ofmethane feedstock would be needed to drive the process. In addition tohydrogen as a major product, the process produces a very importantbyproduct: clean carbon.

Reference should now be made to FIG. 1 which illustrates the inventiveconcept by providing a simplified schematic diagram of the process. Apreheated stream of a hydrocarbon feedstock enters the thermocatalyticreactor 1 where it is thermocatalytically decomposed (pyrolyzed) atfluidized bed temperatures of approximately 700–approximately 1400° C.(preferably approximately 850–approximately 1000° C.) and pressureapproximately 1–approximately 50 atm (preferably, approximately1–approximately 25 atm) over a moving (e.g. fluidized) bed of thecatalytically active carbon particulates. The residence time within thereaction zone is approximately 0.1–approximately 600 sec. (preferably,approximately 1–approximately 60 sec.). The hydrogen-containing gas(HCG) after the reactor 1, a cyclone 2 and a heat exchanger 3 isdirected to a gas separation unit (GSU) 4, where a stream of hydrogenwith at least 99.0 v. % purity can be under appropriate processconditions as disclosed herein is separated from the gaseous stream. Agas separation membrane, a pressure swing adsorption (PSA) system, acryogenic absorption (or adsorption) unit, or any other system capableof separating hydrogen from hydrocarbons, could be employed as GSU.

The concentration of hydrogen in the HCG after the reactor 1 depends onthe hydrocarbon feedstock, the temperature and the residence time andvaries in the range of approximately 30–approximately 90 v. %, with thebalance being methane and higher hydrocarbons (C₂+, including ethyleneand other unsaturated and aromatic hydrocarbons). A hydrogen-depletedgas (HDG) consisting of CH₄ and C₂+ hydrocarbons, is recycled to thecatalytic reactor 1. The concentration of gaseous olefins in HDG dependson the feedstock and could reach approximately 40 v. %. It is one of theimportant findings of this invention that the decomposition ofunsaturated and aromatic hydrocarbons generates catalytically activecarbon species which provoke and facilitate the methane decompositionreaction into hydrogen and carbon. It has been found that recycling ofHDG (containing olefins and aromatic hydrocarbons) from the GSU 4 backto the reactor 1 sustains the high catalytic activity of the carboncatalyst during the process via in-situ generation of catalyticallyactive carbon species. Product-carbon (coke) is withdrawn from thebottom of the fluidized bed reactor 1 in the form of carbon particulates(with a size>approximately 100 microns). A fraction (approximately20–approximately 30%) of carbon is ground into fine (<approximately 100microns) powder (preferably, <approximately 20 microns) in a grinder 5and is directed to a heater 6 where it is heated to approximately900–approximately 1500° C. (preferably, approximately 950–approximately1200° C.), activated, and recycled to the reactor 1.

The heat input necessary to drive the endothermic process can beprovided by burning a portion of carbon with air in a heater 6.Alternatively: it could be done by combusting a part (approximately 10%)of the hydrocarbon feedstock; or a portion (approximately 10%) of theHDG; or a portion (approximately 10–approximately 15%) of the HCG afterthe reactor 1; or, a portion (approximately 15%) of hydrogen in a heater6. The alternative options are preferable, since they also allow thereactivation of the carbon catalyst via surface gasification reactionswith the products of hydrocarbon or hydrogen combustion: CO₂ and H₂O(external activation). At high temperatures (such as approximately 1000°C.) combustion (flue) gases, containing H₂O and CO₂, activate the carbonsurfaces by gasifying carbon and increasing its surface area.Alternatively, heat to the reactor can also be provided by partialoxidation of aromatic hydrocarbons (e.g. benzene, toluene, naphthalene)produced as byproducts during pyrolysis of propane and liquidhydrocarbon feedstocks. This would also result in a simultaneousproduction of catalytically active carbon black particles, which willstick to the recycled carbon particles and be directed from a heater 6to a reactor 1. Thus, a provision is made within this disclosure tointernally (in-situ) and externally activate the carbon catalyst for thepurpose of sustainable internal and external activation would increasethe catalytic activity of carbon particles at least one order ofmagnitude. It has also been found for this novel process that thepresence of sulfur in the hydrocarbon feedstock is not only harmless butactually helps to sustain catalytic process via intermediate formationof HS* radicals that actively attack hydrocarbon molecules of thefeedstock. This implies that there is no need for a very costlydesulfurization step before thermocatalytic conversion of sulfuroushydrocarbon feedstocks. This is in a drastic contrast to conventionalcatalytic reforming and partial oxidation processes which requirecomplete desulfurization of a feedstock to ppm levels. Sulfur ends up inthe form of elemental sulfur which could be condensed into solid productand conveniently removed from the technological streams.

Thus, due to low endothermicity of the process, elimination of severalgas conditioning stages, the overall CO₂ emission from the proposedprocess would be at least one order of magnitude less than fromconventional processes. It should be noted that the process couldpotentially be completely free of CO₂ emissions, if a portion ofhydrogen is used as a heat source.

One modification to the process relates to the integration of thethermocatalytic reactor with a fuel cell (FC) 7 (see FIG. 2). Thismodification would be particularly advantageous if FC is an end-user forhydrogen produced in the process (electric power production scenario).Another potential advantage of this integrated scheme relates to thepossibility of direct usage of CO/CO₂-free effluent gas in FC 7 withoutcomplex and expensive gas conditioning stages (e.g. water gas shift,preferential oxidation, and the like.) required by conventional fuelreformation systems. This is especially important for polymerelectrolyte membrane (PEM) and alkaline type FCs which are prone todeactivation by small amounts of CO and CO₂, respectively. The HCG aftera reactor 1, a cyclone 2 and a heat exchanger 3 enters the anodecompartment 9 of FC 7. Air is introduced into the cathode compartment 10of FC 7. The anode and cathode compartments of FC 7 are separated by amembrane 8. Hydrogen is absorbed by FC (via electrochemical reactions onthe anode surface resulting in the production of electricity 11),whereas, unconverted methane and C₂+ hydrocarbons are recycled to thereactor. Thus, the integrated process takes advantage of both internaland external activation of carbon catalyst. The rest of the embodimentis similar to that described in FIG. 1.

As earlier noted, the major problem with the decomposition of methaneover carbon (or any other) catalysts relates to their gradualdeactivation during the process. A process has been found which improvesthe activity and stability of carbon catalysts during thethermocatalytic process. The sustainability of the thermocatalyticprocess with regard to continuous, efficient and stable production ofboth hydrogen and carbon from a variety of hydrocarbon fuels (including,sulfurous fuels) is as noted another important aspect of the inventionas will be further exemplified.

In Examples 1–6 the original catalytic activity (that is, without anyadditional activation) and relative stability of 3 major types of carbonmaterials (activated carbon, carbon black and graphite) were determinedusing methane, propane, gasoline and diesel fuel as feedstocks.

EXAMPLE 1

A sample of activated carbon DARCO® KB-B produced from hardwood (NORITAmericas Inc.) with surface area of 1,500 m²/g, total pore volume of 1.8ml/g and particle size of 150 μm was used in this example. 030 g of dryactivated carbon (AC) was placed in a 5.0 ml quartz microreactor (a thinbed of carbon material ensured low pressure drop). The reactor wasmaintained at a constant temperature of 850° C. and atmosphericpressure. The reactor was purged with an inert gas (Ar) at 850° C. for30 min. (to remove moisture and entrapped air from the catalysts) beforeintroduction of methane. Methane (99.99 v. %) entered the catalyticreactor at a constant flow rate of 5.0 ml/min. The flow rate of theeffluent gas after the reactor was measured with the accuracy of 5%.Carbon samples were weighed before and after experiment with theaccuracy of 5%. Analysis of methane decomposition products was performedgas chromatographically. Methane decomposition rates (MDR) weredetermined from methane concentrations in the influent and effluentgases (adjusted to corresponding flow rates). The initial MDR (measuredat 80^(th) second, after the introduction of methane into the reactor)was equal to 2.04 mmole/min·g. MDRs were measured every 6–8 min, untilthe end of experiment (usually 90 min). Methane conversion rate afterone hour was equal to 0.65 mmole/min·g, which corresponds to 3.1 folddecrease. It should be noted that in most experiments (with AC and othercarbon catalysts) a quasi-steady state process was established overperiod of one after the onset of the process. Hereafter, a quasi-steadystate (QSS) of the process relates to the time interval during which theprocess parameters (e.g. conversion, concentration of pyrolysis productsin the effluent gas, flow rates) remain unchanged (within the margin of10%). No traces of CO and CO₂ were detected in the effluent gas.

EXAMPLE 2

The experimental conditions for the examples 2 are similar to those ofthe Example 1, except, carbon black (CB) Black Pearls2000 (CABOT Corp.)with the surface area of 1500 m²/g and particle size of 0.012 μm wasused as a catalyst. The initial MDR and MDR after one hour were equal to1.15 and 0.69 mmole/min·g, respectively (corresponding to 1.7 folddecrease in catalytic activity).

EXAMPLE 3

The experimental conditions for the Examples 3 are similar to those ofthe Example 1, except, graphite with the surface area of 10–12 m²/g andparticle size of 50 μm was used as a catalyst. The initial MDR and MDRafter one hour were 0.07 and 0.06 mmole/min·g, respectively. It isevident from Examples 1–3 that activated carbon sample exhibited highestinitial catalytic activity in methane decomposition reaction, whereas,carbon black showed somewhat lower initial activity, but betterstability. Graphite showed very poor catalytic activity towards methanedecompositions.

EXAMPLE 4

0.30 g of carbon black (XC-72) was placed in the quartz reactor with thevolume of 10 ml. The reactor temperature was maintained at 800° C.during the entire experiment. The reactor was purged with Ar (to removemoisture and entrapped air from the catalyst), and propane wasintroduced into the reactor at the flow rate of 5.2 ml/min. A QSS rateof propane pyrolysis was established after 20 min, and it lasted until95^(th) min of the process. During QSS period propane was quantitatively(100% conversion) converted into pyrolysis gas with the averagecomposition presented in Table 1. A flow rate of the effluent gas wasaveraged at 14.5 ml/min. After 90 min, both propane conversion andhydrogen concentration in the effluent gas started to graduallydecrease. Simultaneously, the concentration of ethylene and propylenestarted to increase, and aerosol-like product appeared in the downstream of the reactor.

EXAMPLE 5

The experimental set-up similar to Example 4 was employed in thisexperiment. 0.30 g of activated carbon (hardwood) was used as acatalyst. Gasoline was introduced into the reactor (via an evaporator)by a syringe pump with the flow rate of 1.62 ml/h (liquid). The reactortemperature was 800° C. QSS was established between 20^(th) and 80^(th)minutes of the process, followed by gradual decrease in pyrolysis yield.The average flow rate of pyrolysis gas was 18.5 ml/min. The averagecomposition of gasoline pyrolysis gas is presented in Table 1.

EXAMPLE 6

In this experiment diesel fuel was used as a feedstock. Diesel fuel wasdirectly added to the reactor at flow rate of 1.8 ml/h (liquid) bysyringe pump. The temperature of the reactor was maintained at 780° C. 1g of carbon catalyst (AC coconut, 9–16 mesh) was mixed with 0.5 g ofactivated alumina (9–16 mesh). QSS was established between 40^(th) and120^(th) min of the process. The average flow rate of pyrolysis gas 15.2ml/min. The results are presented in Table 1.

TABLE 1 Example Hydro- Conversion, Pyrolysis gas composition*, v. % No.carbon % H₂ CH₄ C₂H₆ C₂H₄ C₃+ 4 Propane 100 50.8 38.1  2.1  8.9 0.1 5Gasoline 100 48.2 38.1  1.8 11.2 0.7 6 Diesel fuel 100 31.2 34.1 12.419.2 3.1 *This represents an average composition of pyrolysis gas duringquasi-steady state pyrolysis of hydrocarbons

The objective of Examples 7–9 is to demonstrate the feasibility of usingfluidized bed reactors for thermocatalytic decomposition of hydrocarbonsover carbon particulates.

EXAMPLE 7

0.2 g of carbon black Black Pearls2000 (preliminarily sieved to removelarge aggregate particles) was placed in a quartz reactor (volume of thereaction zone 10 ml). The temperature of the reactor was maintained at950° C. The reactor was purged with Ar for 30 min at this temperature toremove moisture and entrapped air from the catalyst. A stream of methanewas introduced into the reactor from the bottom such that the adequatefluidization of carbon particles was maintained at the flow rate of 15ml/min. Methane decomposition gas exited from the upper part of thereactor via ceramic wool filter. QSS of methane decomposition lastedfrom 30^(th) to 240^(th) min of the process. The average methaneconversion during QSS was 23.5%. The effluent gas flow rate and methaneconversion rate averaged at 18.5 ml/min and 0.72 mmole/min·g,respectively. The average composition of the effluent gas is presentedin Table 2. Amount of carbon produced 0.11 g/h.

EXAMPLE 8

The experimental conditions are similar to Example 7, except propane wasused as a feedstock. QSS was maintained from 10 to 60^(th) min of theprocess. The exit flow rate was 34 ml/min. It should be noted thatimmediately after QSS period we observed condensation of the crystals ofnaphthalene on the cold surfaces down stream the reactor. Naphthalenewas identified and quantified by spectrophotometric method (ShimadzuUV-2401 PC). The yield of naphthalene produced during the entireexperiment (2.5 h) was 0.15 mol. %. The amount of carbon produced was0.35 g/h. The results are presented in Table 2.

EXAMPLE 9

The experimental conditions are similar to the Example 7, exceptCH₄—C₃H₈ (3:1 by volume) mixture was used as a feedstock. Themethane-propane mixture was used as a surrogate for natural gas. QSS wassustained from 15^(th) to 90^(th) min of the process. The exit flow ratewas 44.5 ml/min. Amount of carbon produced 0.15 g/h. The results arepresented in Table 2.

TABLE 2 Ex- Temper- Flow Conver- ample Hydro- ature, rate, sion,**Gaseous products*, v. % No. carbon ° C. ml/min % H₂ CH₄ C₂H₆ C₂H₄ C₃+ 7CH₄ 950 15.0 23.5 38.1 61.8 0 0.1 0 8 C₃H₈ 950 15.0 100.0 62.1 35.0 0.52.4 0 9 CH₄—C₃H₈* 950 20.0 100.0*** 52.7 46.3 0.2 0.8 0 *CH₄—C₃H₈mixture was used as a surrogate for natural gas **These data relate toQSS conditions ***Conversion relates to propane

The following Examples 10–15 provide the evidence of internal activationof carbon catalysts. Examples 10–12 are concerned with the relativecatalytic activity of carbons produced by decomposition of ethylene,benzene and naphthalene (which are most important byproducts of TD ofhydrocarbons) in methane decomposition reaction. Examples 13–14 evidencethe increase in methane decomposition rate due to the presence of smallamounts of benzene, gasoline and hydrogen sulfide in the feedstock.Thermal decomposition of hydrocarbons was conducted over an inertsupports, such as alumina and silica gel, in order to eliminate possiblecatalytic effect of the substrate on methane decomposition.

EXAMPLE 10

0.030 g of activated γ-alumina (surface area 80–120 m²/g) was placed ina quartz reactor (volume 5 ml). The reactor was purged with Ar for 0.5 hat 850° C. to remove moisture and entrapped air from alumina. Methanewas introduced into the reactor at flow rate of 5.0 ml/min and thermallydecomposed for 1 h until QSS was established (at 850° C.). Methaneconversion rate corresponding to QSS was 6.3 μmole/min. At this time,the reactor was purged with Ar for 15 min to remove methane from thereactor. This was followed by the pulse of 1.0 μmole of ethylene intothe reactor at 850° C. At these conditions all the ethylene introducedwas decomposed into hydrogen and carbon. The reactor was purged with Arfor 15 min and methane was introduced into the reactor at the originalflow rate of 5.0 ml/min (at 850° C.). Methane decomposition rateincreased to 10.8 μmole/min, which is 1.7 times higher than QSSdecomposition rate. Over period of 30 min, however, methanedecomposition rate gradually dropped to 6.8 μmole/min (which is close tothe QSS value). The procedure was repeated twice and every time weobserved a similar jump in methane decomposition rate after introductionof a pulse of ethylene. These data indicate that carbon produced bydecomposition of ethylene is catalytically more active than the oneproduced from methane.

EXAMPLE 11

The experimental conditions are similar to those of the Example 10,except, the pulse of benzene (1.0 μmole) was introduced into the reactorinstead of ethylene. In this case methane decomposition rate jumped from6.0 to 12.1 μmole/min.

EXAMPLE 12

The conditions are similar to those of the Example 10, except, 0.1 μmoleof naphthalene was decomposed over alumina surface before introductionof methane. This resulted in the increase in methane decomposition ratefrom 6.4 to 17.0 μmole/min.

EXAMPLE 13

0.03 g of silica gel (surface area 600 m²/g) was placed in a quartzreactor with the volume of 5 ml. The reactor was purged with Ar for 0.5h at 850° C. to remove moisture and entrapped air from silica gel.Methane was introduced into the reactor (850° C.) at flow rate of 5.0ml/min for 20 min (until QSS was established). Corresponding methanedecomposition rate was 0.2 μmole/min. This was followed by theintroduction of methane-benzene (5 v. %) gaseous mixture into thereactor at the same temperature and flow rate. It was found that in thepresence of 5 v. % benzene methane decomposition rate was 1.5 μmole/min(7.5 fold increase).

EXAMPLE 14

The experimental conditions were similar to 13, except, benzene wasreplaced by gasoline. 4 fold increase in methane decomposition rate wasobserved in the presence of 5 v. % of gasoline vapors.

EXAMPLE 15

In this example, the effect of small amount of H₂S on methanedecomposition rate is demonstrated. A 0.1 g of carbon black BlackPearls2000 was placed in a quartz reactor (volume 5 ml). The reactor waspurged with Ar for 0.5 h at 900° C. Methane was introduced into thereactor (900° C.) at flow rate of 5.0 ml/min for 1 h (until QSS wasestablished). Corresponding methane decomposition rate was 41.7μmole/min. This was followed by the introduction of CH₄—H₂S (3 v. %)mixture into the reactor at the same temperature and flow rate. Theaverage methane decomposition rate over the period of 1 h was 45.8μmole/min (note that the increase in methane decomposition rate wasgreater than the margin of error).

EXAMPLE 16

The objective of the Example 16 is to demonstrate the possibility ofactivation of carbon catalyst by hot hydrocarbon combustion gasescontaining CO₂ and water vapors (external activation). A 0.2 g of carbonblack Black Pearls2000 was placed in a quartz reactor (volume 15 ml).The reactor was purged with Ar for 0.5 h at 850° C. Methane wasintroduced into the reactor (850° C.) at flow rate of 10.0 ml/min for 80min (until QSS was established). Corresponding methane decompositionrate was 35.5 μmole/min. The reactor was purged with Ar for 15 min atthe same temperature. This was followed by passing over the carboncatalyst (at 950° C.) the hot combustion gases from a propane burner for10 min. The reactor was purged with Ar, and methane was introduced againinto the reactor at 850° C. and the original flow rate. Methanedecomposition rate was measured at 116.2 μmole/min (3.3 fold increasesin methane decomposition rate).

Thus, the Examples 1 through 16 clearly demonstrate the technicalfeasibility of the approach. The major aspects of the process of theinvention were verified through laboratory-scale tests The subjectinvention is directed to sustainable catalytic decomposition of anyhydrocarbon feedstock (from natural gas to crude oil) into hydrogen andcarbon at temperatures well below those characteristic of conventionalthermal decomposition processes (by several hundred degrees).

The subject invention focuses on the means to produce CO/CO₂-freehydrogen and to drastically reduce CO₂ emissions from the process.Relatively low endothermicity of the hydrocarbon decomposition reactions(comparing to steam reforming), the absence of oxidants (air and steam)in the reaction zone, and the freedom from additional gas conditioningstages (e.g. water gas shift, preferential oxidation, CO₂ removal) wouldallow to reach this goal.

The subject invention takes advantage of relatively high catalyticactivity of carbon species produced by decomposition of unsaturated andaromatic hydrocarbons. In this case, decomposition of hydrocarbons withthe low activation energy (e.g. ethylene, aromatics) would inducedecomposition of the hydrocarbon with the high activation energy (e.g.methane). Unsaturated and aromatic hydrocarbons are present in thepyrolysis gases of different hydrocarbons and mixtures of hydrocarbons(including, NG); their recycling to the reactor would provide the meansto sustain high catalytic activity of carbon catalysts (via internalactivation).

The subject invention is also concerned with the possibility of externalactivation of carbon catalyst during thermocatalytic decomposition ofhydrocarbons. This could be achieved via surface activation of thecarbon catalyst by hot combustion (flue) gases during heating thecatalyst.

The subject invention is directed to processing sulfurous hydrocarbonfeedstocks (including, H₂S-containing NG) without need for theadditional purification. Not only sulfur compounds do not poison thecarbon catalyst, but they slightly activate the catalytic process viaintermediate production of active radicals.

Lastly, the subject invention takes advantage of the integration of thesustainable CO₂-free thermocatalytic process with a fuel cell for thepurpose of production of electricity and pure carbon.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

1. An apparatus for generating electricity and sustainable CO₂-freeproduction of hydrogen and carbon via continuous thermocatalyticdecomposition of hydrocarbons over carbon-based catalyst in air and/orwater-free environment, employing continuous reactivation of thecatalyst, comprising the combination of: (a) a thermocatalytic reactorwith a moving bed of carbon particulates; (b) means for purging themoving bed of carbon particulates of moisture and air; (c) means forrecovering hydrogen-containing gas from the reactor; (d) means forseparating the hydrogen-containing gas of step (c) into a first portionof pure hydrogen and a second portion of hydrogen-depleted gas; (e)means for recycling at least a portion of hydrogen-depleted gas to thereactor to sustain high catalytic activity of the carbon catalystin-situ; (f) means for recovering carbon particles from the reactor; (g)means for disintegration of carbon particles of step (f); (h) means forheating of carbon particles to provide externally activated catalystthat is recycled to the reactor; (i) means for recovering pure hydrogenfrom a stream; and (j) means for transporting the pure hydrogen intoanode of a fuel cell, whereby electricity is generated.
 2. The apparatusof claim 1, where the thermocatalytic reactor with a moving bed ofcarbon particulates is a fluidized bed reactor.
 3. The apparatus ofclaim 1, where the carbon particulate is carbon black.
 4. The apparatusof claim 1, where the means for recovering pure hydrogen is a membranegas separation unit.
 5. The apparatus of claim 1, where the means fordisintegration is a grinder.
 6. The apparatus of claim 1, where the fuelcell for generating electricity is a polymer electrolyte membrane fuelcell.